Do you think i charge to less for dickpics?

Hello! i have some subs that enjoy sending me dickpics, they don't expect anything from me, i charge 4$ for everypick they send, sometimes i have 10-20 followers daily that send me dickpics(they don't want rating, just simply spamming me with dick pics) you think i should charge more, or is a fair price as they don't ask for a reply?